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Look, for instance, at the population of Belgium, Holland, and Lower Germany, and notice how dense it is upon the alluvial flats where the Meuse, Rhine, and other rivers approach the sea. It is just the same in Britain. London lies on the great alluvial flats of the Thames, Glasgow on the Clyde, Liverpool on the Mersey. In China it is the Yang-tze-kiang valley (especially near its mouth); in India, the Ganges, of lower Bengal, and in the Argentine the La Plata River, which show the greatest accumulations of humanity. In every case it is the rich flat alluvium, which is exceedingly fertile when drained and cultivated, that has originally attracted so many people.